Nonsynchronous transfer apparatus

ABSTRACT

Closed loop conveyor apparatus for moving pallet supported workpieces comprising a pair of endless chain conveyors having guide rollers engaging guide rails, and pallet support rollers contacting the underside of the pallets. As a work station is approached, the support rollers may be rotated to slow down the speed of the pallets relative to the conveyors so that indexing means may remove the pallets from the conveyors and properly align the pallets at the work station. After a machining or assembly operation is completed, the pallets are replaced on the support rollers which may be rotated to smoothly increase their speed relative to that of the conveyors.

United States Patent Buldini 1 Sept. 12, 1972 [54] NONSYNCHRONOUSTRANSFER APPARATUS [72] Inventor: Daniel A. Buldini, Revere, Mass.

[73] Assignee: Polaroid Corporation, Cambridge, Mass.

[22] Filed: July 16, 1970 [21] Appl. No.: 55,463

[52] US. Cl. ..l98/l9, 198/110, 198/183 [51] Int. Cl ..B65g 15/10, B65g21/12, B23q 5/22 [58] Field of Search ..l98/l9,110,183

[56] References Cited UNITED STATES PATENTS 2,257,230 9/1941 Drake..l98/183 2,762,496 9/1956 McCaul ..l98/183 2,953,234 9/1960 Abendschein..l98/183 X 2,959,273 11/1960 Sykes ..198/l83 FOREIGN PATENTS ORAPPLICATIONS 731,455 6/1955 Great Britain ..l98/l8l PrimaryExaminer-Edward A. Sroka Attorney-Brown and Mikulka and Sheldon W.Rothstein 5 7 1 ABSTRACT Closed loop conveyor apparatus for movingpallet supported workpieces comprising a pair of endless chain conveyorshaving guide rollers engaging guide rails, and pallet support rollerscontacting the underside of the pallets. As a work station isapproached, the support rollers may be rotated to slow down the speed ofthe pallets relative to the conveyors so that indexing means may removethe pallets from the conveyors and properly align the pallets at thework station. After a machining or assembly operation is completed, thepallets are replaced on the support rollers which may be rotated tosmoothly increase their speed relative to that of the conveyors.

5 Claims, 6 Drawing Figures PATENTEDsEP 12 m2 SHEET 1 [1F 6 INVENTOR.DANIEL A. BULDINI WWW m1 WWW ATTORNEYS PATENTEDsEP 1 2 m2 SHEET 2 [1F 6INVENTOR. DANIEL A.BULD|N| 705mm a/nd W and PATENTEDSEP 12 I9723.690.433

sum 3 or 6 INVENTOR.

DANIEL A.BULD|N| @Jcowwz and m and PATENTEDSEP 12 I912 3590.433

SHEET 0F 6 1 WORK STATION 1 FIG. 4

INVENTOR. DANIEL A. BULDINI E/ww n MM @Y/Mdm 716 130mm ATTORNEYSPATENT'EDSEP 12 m2 SHEET 5 BF 6 FIG.5

INVENTOR. DANIEL A. BULDINI m WW ATTORNEYS PATENT ED SEP 12 m2 SHEET 8BF 6 FIG.6

INVENTOR. DANIEL A. BULDINI Wm WM ATTORNEYS NONSYNCHRONOUS TRANSFERAPPARATUS The present invention relates to a closed loop conveyor systemfor nonsynchronously moving workpieces between successive automated workstations. This system is useful both where the workpiece is to have amachining operation performed on it at the work station and also wherethe workpiece constitutes a subassembly and additional parts areassembled thereon at the respective work stations. It is capable ofmaking turns from a straight path in order to be accommodated tosubstantially any plant layout and eliminates return tracks, etc., sinceany segment of the closed loop may be utilized as a work station.

It is well known in the art that where a number of separate work stepsor assembly operations are to be performed in a given sequence, it isoften desirable to move the workpiece from station to station on someform of conveyor apparatus.

In contrast to one known general type of conveyor system in which theconveyors are synchronously driven and periodically simultaneouslystopped at reselected stations, the system of the present invention isof the type in which the conveyors run substantially continuously in anendless path and the pallets carrying the workpieces may be stopped andremoved from the conveyors at work stations and returned to theconveyors after the completion of the machining or assembling operationwhich is carried out at the work station.

The spacing of the pallets on the conveyor may be varied throughout thesystem depending upon the time requirements of the operations which willbe carried out at the respective work stations. For example, for anautomatic operation which is relatively fast, simple and trouble-free,the approaching pallets may be spaced relatively far apart. On the otherhand, for an operation which is more time consuming, the palletsapproaching this station may be spaced relatively close together.

The nonsynchronous pallet conveying system of the invention isapplicable to convey articles to successive automatic machiningoperations at successive work stations or to successive automaticassembly operations or a combination thereof, and is also useful wheremanual operations are combined with automatic machining or assemblyoperations.

In accordance with a presently preferred embodiment of the invention,the pallet conveyor comprises a pair of parallel endless chains composedof pivotally interconnected links. Each chain conveyor has spaced pairsof upstanding flanges integrally attached to its upper portions. Fixedpins extend through apertures in these flanges and rotatable guiderollers are disposed on the pins in contact with guide tracks. Rotatablepallet support rollers are also disposed on the fixed pins and supportand underside of the pallets. At selected locations in the system thespeed of the pallet may be changed by imparting relative rotation to thesupport rollers. In order to decelerate the pallets, the rollers arerotated to impart to the pallets a force component which acts inopposition to the direction of movement of the conveyor. Similarly, toaccelerate the pallets, the rollers are rotated to impart to the palletsa force component which acts on the direction of movement of theconveyors. Such rotation may be imparted to the guide rollers by passingthese rollers into contact with endless belts or similar means. In thisfashion, the pallets may be decelerated as they approach a work stationand in fact stopped at the work station even though the conveyorcontinues to move without interruption. At the work station, indexingmeans, which may be actuated either pneumatically, hydraulically orelectrically, contacts the pallets to elevate them off of the conveyorwhile the machining or assembly operation is carried out. Thereafter,the pallets are returned to the conveyor and transferred to the nextwork station.

It is a primary object of the present invention to provide an improvedpallet conveyor system for moving workpieces or other articles from onework station to another.

Another object of this invention is to provide a closed loop conveyorsystem capable of conforming to substantially any plant layout.

A further object is to provide a pallet conveyor system having palletsupport rollers connected to the conveyor chains and adapted to eitheraccelerate or decelerate the pallets as required in the system.

The above and other objects, features and advantages of the inventionwill become more apparent as this description proceeds.

IN THE DRAWINGS FIG. 1 is a perspective view partly in section of oneembodiment of a pallet conveyor system in accordance with the presentinvention.

FIG. 2 is a perspective view of a section of an endless conveyor chainutilizing the present invention.

FIG. 3 is a vertical cross-sectional view of the embodiment of FIG. 1taken at a point contiguous to a work station.

FIG. 4 is a diagrammatic representation of how the speed of a pallet isadjusted relative to the speed of the conveyor by imparting rotation tothe pallet support rollers.

FIG. 5 is a vertical cross-sectional view similar to that of FIG. 3 butof another embodiment of the present invention.

FIG. 6 is a view primarily in vertical cross-section of the embodimentof FIG. 5 with one of the pallets being shown in an indexed position ata work station.

Referring now to the drawings, and more particularly to FIG. 1,reference numeral 10 generally designates the conveyor apparatus of onepresently preferred embodiment of the invention upon which pallets 12are conveyed in a generally horizontal position. In this embodiment,each pallet has mounted on it a pair of workpieces 14 which are shown indot-dash lines. The conveyor carries the pallets past a plurality ofwork stations. A pair of opposed work stations 16 positioned tosimultaneously act on the two work pieces on a given pallet are shown inFIG. 1 by way of illustration. The pallets preferably have spacers orbumpers 15 at their forward edges to lessen impact between adjacentpallets.

Referring to FIG. 2, the conveyor system includes a pair of spacedparallel endless roller chains. Each chain comprises a plurality ofinterconnected links constituted by an upper plate 18 and a lower plate20 which are pivotable connected to the adjacent link by a headed pin22. For the sake of clarity, the upper and lower plates of the rearmostof the two links shown in FIG. 3 are designated by reference numerals18' and 20', respectively. A guide member 24, which is preferablyrotatable, is positioned on each pin 22 spaced from the upper and lowerplates by washers 26 and 28.

A pair of upstanding vertical flanges 30 are integrally connected toeach upper plate at opposite sides thereof and each flange has anaperture 32 which is aligned with the aperture in its mating flange. Afixed rod 34 extends through each pair of apertures 32 with its endsextending outwardly beyond the flanges. A guide roller 36 is freelyrotatably positioned at each end of each rod 34 and is spaced fromadjacent flange 30 by a bearing 38. The outermost ends of rods 34, thatis, the left-hand side of the left-hand conveyor of FIG. 3 and therighthand side of the right-hand conveyor, project further than theother ends of the rods and also have larger pallet support, rollers 40freely rotatable thereon, and spaced from the adjacent support rollers22 by bearings 42. Lock washers 44 or other comparable means are placedupon the ends of the rods 34 to keep the rollers in position.

As best seen in FIG. 3, the guide rollers 36 move along inside andoutside guide rails 46 and 48. These guide rails are integrallyconnected to a horizontal spacer plate 50, which is mounted on thesupport pad 52 of vertical post 54.

To maintain the conveyors in parallel alignment, the horizontal rollers24 which are disposed on the vertical pivot pins 22 are located betweenthe inner and outer guide rails 46 and 48.

For safety sake, the conveyors are substantially enclosed on each outerside by an essentially right angle shaped casing member 56 which has itsshort side united to the underside of support plate 52 and has its longside extending vertically almost to the underside of the pallets.Similarly, the conveyors are substantially enclosed on the top byinverted right-angle shaped casing members 58 which have one side unitedto the side of a respective inner guide rail 46 and have the other sideextending generally horizontally below the path of conveyor travelnearly into contact with the pallet support rollers 40.

When the roller chains are driven by a suitable drive means, it isevident that the rollers will move along the guide rails 46 and 48thereby moving the pallets which are resting on top of the supportrollers 40 along the path of the conveyor system.

As a pallet approaches a work station, it may be advantageous todecelerate the pallet to facilitate possible removal of the pallet fromthe conveyor at the work station. Similarly, after the completion of theoperation at the work station, the pallet may be returned to theconveyor and accelerated to the speed of the conveyor. These steps ofdeceleration and acceleration may be accomplished by regulating therotational speed of the pallet guide rollers 40. In general, the supportrollers 40 will tend to carry the pallets 12 along without any rotationof the support rollers so that the speed of the pallets corresponds tothe speed of the conveyors. As a work station is approached, the palletsmay be decelerated by causing the rollers 40 to come into contact withdriven belts 60 mounted on drive rollers 62. Referring to FIG. 3,assuming that the conveyors are moving upwardly out of the plane of thesheet of drawing, the belts 60 are driven at a speed in excess of thatof the conveyors with their upper passes similarly moving upwardly outof the plane of the sheet. Since the belts 60 are in contact with therollers 40 this imparts rotation to the rollers 40 which concommitantlyimparts to the pallets 12 a component of force which acts in a directionopposite to the direction of movement of the conveyors therebydecelerating the pallets relative to the conveyors.

The regulation of the speed of the pallets is somewhat schematicallyillustrated in FIG. 4. As represented therein, with the conveyors movingat a uniform speed in the direction of the arrow A, belt 60 is rotatedin the same direction but at a greater speed so that roller 40,contacted by belt 60, provides a decelerative force to pallet 12.

By appropriate regulation of the relative speeds of the conveyors and ofbelt 60, the pallet may not only be decelerated, but the pallet may bemade to completely stop when the velocity of belt 60 is twice thevelocity of the chain conveyors. The speed of belt 60 may be furtheradjusted after the pallet has slowed down to a speed at which it, ineffect, becomes stationary of the work station.

Suitable indexing means to be described hereinafter may remove thepallet from the conveyor to enable the workpiece to undergo machining orassembling operations, and thereafter return the pallet to the conveyor.When the work is completed, the pallet then preferably passes into aregion in which the rollers 40 are contacted by an endless belt 61trained about drive rollers 63 to provide an accelerative force to thepallet relative to the chain conveyors as it travels away from the workstation. This belt is similar in configuration and construction to belt60 and is moving in the same direction as and at a speed slower thanthat of the conveyors. Whenever the belt providing speed control to thepallets travels at a speed greater than the chain conveyors, the palletswill decelerate relative to the chain conveyors. When the belt travelsat a speed slower than the chain conveyors, the pallet will acceleraterelative to the chain conveyors.

It will of course be understood that comparable results could beobtained using endless chains in lieu of the endless belts 60 and 61 inorder to regulate the speed of the pallets.

As shown in FIG. 3, any suitable indexing means may be employed toelevate the pallet above the conveyor, and immobilize it while work isperformed on the workpieces carried on the pallet, and then return thepallet to the conveyor system. By way of example, the indexing means mayinclude a pair of vertically movable members having tapered heads 64which engage within complimentarily shaped recesses 66 in the undersideof the pallet 12 with a supporting surface 68 upon which the palletrests. The indexing members reciprocated vertically upon post 70 whichis actuated either pneumatically, hydraulically or electrically to bringthe pallet in contact with bumper 106. It will of course be appreciatedthat suitable control means, not shown, are provided for controlling theindexing means. For example, the approach of a pallet into position forcommencing the indexing operation may be sensed by a spring biased stopwhich when contacted by the pallet generates an electrical signal, or byphotocells or the like. After the desired operation has been performedupon the workpieces, the end of the work operation may be indicated byan electrical signal generated at the conclusion of the work operationassuming that a machine operation is being performed. Alternatively, thepallets may be returned to the conveyors by lowering of the indexingmeans automatically after a predetermined time cycle has passed.

It is preferred to employ guide means to prevent lateral movement of thepallets and this may be accomplished by providing guides 72 which movein a track formed by the vertical legs of the casing members 58. Theguides 72 are preferably rotatably mounted on shafts 74 which aresecured to the underside of each pallet along its center line, one atthe leading edge and one at the trailing edge thereof.

FIGS. 5 and 6 illustrate another embodiment of the present invention inwhich the roller belt conveyors are disposed to the outside of a pallet76. In this embodiment, like reference numerals are utilized todesignate like parts of the roller conveyors of the previously describedembodiment. As shown in FIG. 5, the pallets are supported upon supportrollers 44' disposed at each side of the pallets. In this embodiment thesupport rollers 44' are the same size as the conveyor guide rollers 36.The guide rollers 36 travel along internal guide rails 73 and along thehorizontal surface of an inverted angle iron 80 disposed at each side ofthe conveyor. The angle irons 80 in conjunction with right-angle shapedcasing members 82 substantially enclose the conveyors for safetypurposes. Guide rails 78 and the lower ends of the angle irons 80 arewelded or otherwise suitably secured to spacers 84, generally less thanabout 2 inches wide and machined to maintain the proper distance betweenthe guide rails 78 and the angle irons 80. The frame members aresupported by transverse horizontal bars 86 which are disposed onvertical posts 88 andbraces 90.

The horizontally disposed guide members 24 of the roller chains arelaterally located between the inner surfaces of the angle irons 80 andthe outer surfaces of guide rails 78 to provide lateral stability forthe conveyors. The speed of rotation of the pallet support rollers 44'is adjusted to decelerate and accelerate of the pallets substantially asdescribed in connection with the previous embodiment. For this reason,the support roller speed adjusting system in indicated diagrammaticallyin FIG. 5 by dot-dash lines and reference numeral 92. It will beappreciated that, like in the previous embodiment, this mechanismemploys one belt contacting the underside of the support rollers 44' tocause deceleration of the pallets as a work station is approached andanother belt to cause acceleration of the pallets leaving the workstation.

Referring now to FIG. 6 in which a speed adjusting mechanism for thesupport rollers is not shown for purposes of clarity, a pallet 76 havinga centrally disposed workpiece 94 covering a central opening 96 in thepallet is shown removed from the conveyor at a work station by suitableindexing means generally similar to that employed in the previouslydescribed embodiment. The indexing means include tapered heads 98 whichengage in holes 100 in the pallet, and which are mounted upon a frame102. This frame is adjusted vertically by actuation of a schematicallyillustrated piston 104. The extent of elevation of the pallet may befurther regulated by providing at each side of the pallet a plurality ofbumpers 106 which contact the top of the pallet. The bumpers may beadjusted vertically via stems threadably disposed in nuts 108 which arerigidly connected to supports 1 10.

For purposes of illustration only, the work station shown in FIG. 6comprises an upper tool holder in which there is mounted a drill orsimilar tool 122. The tool holder is reciprocated by a suitablemechanism 124 to and away from the workpiece 94 by means of suitableautomatic controls in order to perform a work function on the uppersurface of the workpiece 94. At the same time, a tool 112 mounted in atool holder 114 is moved into contact with the lower surface of theworkpiece via a suitable reciprocating mechanism 1 16. The lower tool112 passes through an aperture 118 in the indexing means support 102 andthrough the aperture 96 in the pallet in order to contact the workpiece94.

While presently preferred embodiments of the invention have been shownand described with particularity, it will be appreciated that variouschanges and modifications may readily suggest themselves to those ofordinary skill in the art upon being apprised on the present invention.It in intended to encompass all such changes and modifications as fallwithin the scope and spirit of the appended claims.

What is claimed is:

l. A workpiece conveyor system wherein a plurality of pallets areindependently substantially horizontally transported between a pluralityof work stations disposed along a conveyor line comprising: a pair ofindependent endless roller chain conveyors disposed parallel to oneanother, each of said roller chain conveyors including a plurality ofsubstantially horizontally pivotally interconnected links, andindependently rotatable pallet support rollers; rail means forsupporting said endless roller chain conveyors; guide means engagingsaid endless roller chain conveyors and adapted to ride against saidrail means in order to guide said endless roller chain conveyors along apredetermined path; and means in direct communication with same of saidpallet support rollers to adjust the rate of rotation of said palletsupport rollers in order to regulate the speed of pallets supportedthereby relative to the speed of the chain conveyors.

2. Apparatus according to claim 1, wherein said means to regulate therate of rotation of said pallet support rollers comprises: first endlessbelt means for contacting the periphery of said support rollers toimpart rotation thereto decelerate said pallets relative to the endlessroller chain conveyors; and second endless belt means for contacting theperiphery of said support rollers to impart rotation thereto toaccelerate said pallets relative to the endless roller chain conveyors.

3. Apparatus according to claim 1, further comprising inner and outercasing members substantially enclosing said endless roller chainconveyors. chain 4. Apparatus according to claim 1, wherein said endlessroller chain conveyors are located substantially vertically beneath saidpallets and said pallet support rollers are larger than said guiderollers.

5. Apparatus according to claim 1, wherein said endless roller chainconveyors are disposed laterally of and below said pallets, and saidpallet support rollers are disposed directly beneath said pallets.

1. A workpiece conveyor system wherein a plurality of pallets areindependently substantially horizontally transported between a pluralityof work stations disposed along a conveyor line comprising: a pair ofindependent endless roller chain conveyors disposed parallel to oneanother, each of said roller chain conveyors including a plurality ofsubstantially horizontally pivotally interconnected links, andindependently rotatable pallet support rollers; rail means forsupporting said endless roller chain conveyors; guide means engagingsaid endless roller chain conveyors and adapted to ride against saidrail means in order to guide said endless roller chain conveyors along apredetermined path; and means in direct communicatioN with same of saidpallet support rollers to adjust the rate of rotation of said palletsupport rollers in order to regulate the speed of pallets supportedthereby relative to the speed of the chain conveyors.
 2. Apparatusaccording to claim 1, wherein said means to regulate the rate ofrotation of said pallet support rollers comprises: first endless beltmeans for contacting the periphery of said support rollers to impartrotation thereto decelerate said pallets relative to the endless rollerchain conveyors; and second endless belt means for contacting theperiphery of said support rollers to impart rotation thereto toaccelerate said pallets relative to the endless roller chain conveyors.3. Apparatus according to claim 1, further comprising inner and outercasing members substantially enclosing said endless roller chainconveyors. chain
 4. Apparatus according to claim 1, wherein said endlessroller chain conveyors are located substantially vertically beneath saidpallets and said pallet support rollers are larger than said guiderollers.
 5. Apparatus according to claim 1, wherein said endless rollerchain conveyors are disposed laterally of and below said pallets, andsaid pallet support rollers are disposed directly beneath said pallets.